On 10/26, Russell King wrote:>> I've been toying with a similar patch for ARM, but I keep feeling uneasy> about having interrupts enabled in this path (even though they get enabled> in the depths of the signal handling code.)>> I worry about are race condition like the following:>> syscall enter> ...> syscall returns -ERESTARTNOHAND> check for signal> signal pending, but no handler, setup for restart> interrupt happens, sets need_resched> need_resched set> switch to another thread> ...> something happens which queues SIGIO> switch back to this thread

I don't understand how "interrupts disabled" can help... A signalcan come without preempt_schedule().

> check for signal> signal pending, has handler, but we've setup for a restart> return to userspace> run SIGIO handler> restart syscall>> This feels like it violates the expectations of the syscall being> restarted - which explicitly asks to be restarted only if there wasn't> a handler run.

But this doesn't differ from the case when this signal comes afterthe sycall was already restarted?

> However, that doesn't solve the (probably unsolvable) case where an> ERESTARTSYS syscall is interrupted by a SA_RESTART-marked handler, and> while that handler is running it is then interrupted by a non-SA_RESTART-> marked handler. I think that is far too an obscure case to care about> though.